This invention relates to ink jet printers and, more particularly, to a new and improved ink jet printer having two modes of operation for printing at high quality or high speed.
In ink jet printers, and particularly color printers, the quality of the image produced by the printer depends in part on the spacing between successive lines of ink dots applied from the orifices of the ink jet head. For maximum definition, producing the highest-quality printing, the distance between the lines of dots produced by the ink jet should be very small, for example, about 0.003 inch or 3 mils. On the other hand, the printing time, i.e., the time required to print a segment of paper or other image-receiving medium, depends upon the scanning rate of the ink jet head and the number of lines printed to produce the segment. Thus, ink jet printing can be accomplished more quickly by printing with lines which are spaced farther apart than the spacing required for maximum quality, thereby producing a print having less than the best quality. In some instances, a larger number of nozzles is provided in an ink jet head to increase the printing speed but, where color printing is required, the same increase in the number of nozzles must be provided for each color to provide increased printing speed at maximum quality.
To overcome this problem, it has been proposed, for example, in the Tazaki U.S. Pat. No. 4,580,150, to provide an increased number of ink jet nozzles for ink used to print primary characters and a lower number of nozzles to print nonprimary characters in a different color ink and to print the primary characters at a higher speed than the nonprimary characters. With that arrangement, however, it is not possible to increase printing speed when printing the nonprimary characters, even if maximum print quality is not necessary.